What are the differeces between double stars, variable stars and binary stars?
|Books | Astronomy Picture of the Day | News | Calendars | Star Charts | Observing | Education|
Eclipsing Binary Stars - What are Binary Stars? Most stars are found in groups of stars that are gravitationally bound with each other. The majority of these stars are found in binary systems which are systems of two stars in orbit around a common center of mass.
One can classify binary stars based on their appearance from earth. Stars that are far enough apart to be distinguished from each other are known as visual binaries. Other binaries are too close and far away to be seen separately but can distinguished using the doppler shift of their spectra. These are spectroscopic binaries.
The Formation of Binary Stars - Recent observational investigations of the frequency of occurrence of pre-main-sequence binary stars have reinforced earlier suspicions that "binary formation is the primary branch of the star-formation process". A number of different theories have been proposed to explain the preponderance of binary stars. Klein et al. (1998) show how the direct fragmentation of protostellar gas clouds may occur in early phases of collapse (at cloud densities n = 103 - 1010 cm-3). But at higher densities, clouds are unable to cool efficiently upon contraction. Consequently, direct fragmentation becomes problematical. Because higher mean densities are associated with systems having shorter dynamical times, one is led to consider mechanisms other than direct cloud fragmentation for forming binary systems with orbital periods less than a few hundred years. Here we investigate whether such binaries can form by spontaneous fission of rapidly rotating protostars.
Washington Double Star Catalog (WDS) maintained by the United States Naval Observatory is the world's principal database of astrometric double and multiple star information. The WDS Catalog contains positions (J2000), discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions, and, when available, Durchmusterung numbers and notes for the components of 102,492 systems based on 728,813 means.
The Double Star Library - The Double Star Library hopes to be a means by which various types of binary and multiple star information can be easily disseminated among binary star astronomers in IAU Commission 26 and related commissions. These types of information include (but are not limited to) lists of newly discovered systems or orbits, new astrometric or spectroscopic data for known systems, notices of meetings or observing campaigns, and titles of recently published papers.
© Copyright 2010 - Samuel J. Wormley